The British government is coming under pressure after failing to meet its own deadline to decide whether to hold a judge-led inquiry into the UK’s involvement in post-9/11 human rights abuses.

Three months ago Theresa May offered an apology for MI6’s role in the kidnap and torture of a Libyan dissident and his wife in 2004.

The following month, after a four-year investigation, Westminster’s intelligence and security committee reported that UK intelligence officers had been involved in human rights abuses on hundreds of occasions, but complained that May had prevented key witnesses from giving evidence.

Foreign Office minister Alan Duncan subsequently told MPs that the government would decide within 60 days whether or not to hold an inquiry led by a judge – a deadline that passed last Monday.

Some government lawyers are understood to be concerned that human rights abuses that took place within the context of an international armed conflict could have amounted to war crimes, and that if the UK does not thoroughly investigate, the international criminal court in The Hague could step in.

A number of former government ministers have written to May urging that such an inquiry be held. The former justice secretary Ken Clarke said he was disappointed that the deadline had been missed. “I can only hope this means they are working to finalise the details of the independent judge-led inquiry we need. We still do not know fully what went wrong and why, nor who was responsible,” he said.

Earlier this month five senior MPs and peers who have served in the armed forces – Tories Andrew Mitchell, David Davis and Crispin Blunt, the former Liberal Democrat leader Lord Ashdown and Labour’s Dan Jarvis, wrote to May to say that an inquiry was needed in order to learn from the lessons of the past.

Labour said that it would hold an inquiry, if elected, if the government failed to do so. The shadow attorney general, Shami Chakrabarti, said: “The government has now failed to meet its own deadline for a response to cross-party calls for a judge-led inquiry. At a time when the US president has endorsed the use of waterboarding ‘and a hell of a lot worse’, it has never been more important that the UK stand firm against the use of torture and mistreatment.”

Dan Dolan, head of policy at the human rights group Reprieve said: “Survivors of torture and rendition have waited long enough for the independent inquiry this government promised when it took office eight years ago. Last month a Foreign Office minister promised the House of Commons an announcement would be made ‘within 60 days’.

“Now that window has come and gone without a word from Whitehall, we have to ask what Theresa May is waiting for – and how much longer survivors must hold out for the accountability they deserve.”

A Foreign Office spokesperson said: “The government is carefully considering the intelligence and security committee’s reports into detainee mistreatment and rendition issues and will respond formally in due course. Consideration will also be given to the separate calls for another judge-led inquiry.”